I wasn't able to find a 30 mm fan for assembling and testing CAD models of v6 fan ducts, so I modeled my own using the measurements e3d provides and my own fans.
The holes are for M3 bolts and they are a bit tight, so the screw can make the thread itself. Print without supports, laying on the flat side of the fan.
I also added the .Step files if you want to use it as is or the .FCStd if you want to modify it.
https://e3d-online.zendesk.com/hc/en-us/articles/360017144017-Fan-Drawings
The author marked this model as their own original creation.